Not applicable.
Not applicable.
This invention relates generally to motor-driven fans, and more particularly to a blade assembly for such fans, wherein the blade assembly includes a single blade balanced by a counterweight for rotation on a drive shaft of the fan.
It is known from U.S. Pat. No. 2,079,044, to Santmyer, to provide a fan having a blade assembly presenting a hub sized for receipt on a drive shaft of the fan, a single fan blade protruding radially from the hub in a first direction, and a counter weight protruding radially from the hub in a second direction opposite the first direction. This general type of blade assembly provides numerous advantages over other conventional blade assembly constructions incorporating two diametrically opposed, radially extending blades. For example, by employing only a single blade, the assembly creates less drag, increasing the efficiency of the fan. As such, it is possible for the fan to move more air with the single-blade assembly than if a multiple-blade assembly was used.
Although the conventional single-blade assembly provides such advantages over multiple-blade assemblies, some drawbacks exist. For example, the cost of manufacturing such single-blade assemblies out of metal is prohibitive, and if multiple sizes are to be manufactured, it is necessary to design each independently due to the configuration of the blade and counterweight employed.
It is an object of the present invention to provide a blade assembly for a motor-driven fan, wherein the blade assembly is formed of a single piece of aluminum, zinc or synthetic resin material, and is of a configuration that permits different sizes of blades to be manufactured from a single mold.
Another object of the invention is to provide a blade assembly that provides a counter weight body having a mass that can be varied during or subsequent to manufacture to balance the blade assembly for rotation on a drive shaft of the fan.
A further object of the invention is to provide a method of manufacturing a blade assembly, wherein a single mold is used to produce blades and counter weights of different sizes and masses, reducing the cost of manufacture.
In accordance with these and other objects evident from the following description of a preferred embodiment of the invention, a method of constructing a blade assembly includes providing a mold presenting a hub cavity, a blade cavity protruding from the hub cavity in a first direction, and a counterweight-body cavity protruding radially from the hub in a second direction opposite the first direction, and fitting a removable first mold insert in the blade cavity, the first mold insert filling a portion of the blade cavity remote from the hub cavity. Thereafter, a synthetic resin material is injected into the mold with the first mold insert in place to form a blade assembly having a blade with a dimension in the first direction that is shorter than the dimension of the blade in the first direction would be if the synthetic resin material was injected into the mold with the first mold insert removed.
Preferably, the method also includes the step of fitting a removable second mold insert in the counterweight-body cavity, the second mold insert filling a portion of the counterweight-body cavity so that when synthetic resin material is injected into the mold, the blade assembly formed thereby includes a counterweight body having a mass that is smaller than the mass would be if the second mold insert were removed from the counterweight-body cavity.
By providing a method in accordance with the present invention, numerous advantages are realized. For example, by employing a mold and mold inserts in the manufacture of a blade assembly, it is possible to produce such assemblies of varying sizes with a single mold, substantially reducing the cost of manufacture. In addition, both the blade size and counter weight mass can be modified through the use of inserts, enabling the resulting assemblies to be properly balanced for operation on a fan apparatus.
The blade assembly of the present invention includes a hub presenting a longitudinal aperture adapted for receipt on the fan apparatus, a blade protruding radially from the hub in a first direction, and a counterweight body protruding radially from the hub in a second direction opposite the first direction, wherein the hub, blade and counterweight body are formed of a unitary piece of synthetic resin material. The counterweight body of the assembly can be a solid body or hollow, and provides all or a part of the counter weight necessary to balance the assembly for use. If additional weight is added, it is adhered or fastened to a support surface of the body. Alternately, a cavity can be formed in the body, within which additional weight is received.
By providing a blade assembly in accordance with the present invention, several advantages are obtained. For example, by forming the hub and counter weight body of the assembly as a single unitary part, the cost of the assembly is reduced relative to conventional constructions.